“It sounds funny to say, we saw it, as a family, as just a family wedding,” Kate Middleton‘s younger sister, 30, told Matt Lauer in a two-part interview set to air on Monday and Tuesday.

“I didn’t realize, perhaps, the scale of it, until afterwards,” she continued. “I had to make sure I helped my sister where I should, and look after the bridesmaids and pageboys. But we really saw it as a family getting together and doing their bit.”

The importance of the wedding only set in when she joined her sister and brother-in-law on the balcony following the ceremony.

“It was when we saw crowds rushing around, towards the balcony, and I suddenly was like, ‘Wow, this is pretty special,’ ” she said.

The spectacle surrounding her sister’s big day wasn’t the only thing that caught Middleton off guard. She was also surprised by the attention that her bridesmaid dress, or how she looked in it, garnered.

“It was completely unexpected,” she said. “I think the plan was not really for it to be a significant dress, really just to blend in with the train. I supposed it’s flattering … Embarrassing, definitely. Because it wasn’t planned, the dress was almost supposed to be insignificant.”